Determination of the calcium ground state scattering length by photoassociation spectroscopy at large detunings

Photoassociation spectroscopy was used to determine the s-wave scattering length of Ca-40 atoms in their electronic ground state. Vibrational levels were observed in an extended range of up to 182 GHz below the dissociation limit 4s(2) (1)So-4s4p P-1(1). Thus, the frequency interval was nearly tripled, in which photoassociation was observed compared to previous measurements. The spectra were analyzed by means of quantum mechanical simulations. With the new data it was possible to resolve the discrepancy concerning the ground state scattering length presented in earlier publications [Phys. Rev. A 67, 043408 (2003); Eur. Phys. J. D 26, 155 (2003)]. An improved dipole-dipole coupling constant C Sigma(3) = 0.52306(20) x 10(3) cm(-1) nm(3) is obtained.